i don't want to use a crutch. if my leg was broken sure i would use a crutch. shouldn't i treat my neurotransmitters so kindly. >> charlie: steven warren what are the underlying of this. >> we know genetic plays a role by looking at family histories. schizophrenia occurs in 1% of the normal population but if you have a sibling with schizophrenia your risk goes up to 90%. even more striking is people who are identical twins they share 100% of their genome and the risk is now nearly 50%. what's important is it's not a hundredpercent like it is with simple genetic trait like cystic fibrosis where identical twins, both twins will have the same disorder. here half are discordant or don't share that disease. >> there are other factors playing a role like environmental factors. you see also looking at non-identical twins who are essentially just siblings but yet, they have a higher risk than siblings because they share an environment. we think of complex disease as now having contributions of genome as well as contributions to the environment. it's usually easier find